The goal of the proposed research is to develop the experimental foundation needed for extending the use of ultrasound to characterize the physiological state of tissue. Ultrasound can be used to image the heart non-invasively and non-traumatically with conventional, albeit limited, techniques. However, detailed, quantitative information of how and to what degree the ultrasonic signals are altered by tissue undergoing infarction is not yet available. The present research addresses the need for obtaining information and correlating the findings with an independent biochemical criterion of tissue injury. In the long view, the research proposed should facilitate serial and non-invasive detection, characterization, and perhaps quantification of myocardial injury in vivo. Making use of a method based on the determination of the frequency dependence of ultrasonic attenuation and with a receiving transducer designed to eliminate artifacts due to phase cancellation effects, we are carrying out a statistically significant number of experiments in vitro on myocardial tissue obtained from dogs sacrificed after periods ranging from 15 minutes through 3 months following coronary artery occlusion. Results of these ultrasonic tissue characterization studies will be correlated with an independent, quantitative index of local myocardial ischemic injury based on the depletion of creatine kinase. Methods are proposed for extending the technique to open-chest dogs. Validation of the efficacy and reliability of the proposed ultrasonic tissue characterization technique using animal preparations should lay the groundwork for the development of a system suitable for use in patients. BIBLIOGRAPHIC REFERENCES: "Changes in Ultrasonic Attenuation Indicative of Regional Myocardial Infarction," D.E. Yuhas, J.W. Mimbs, J.G. Miller, A.N. Weiss, and B.E. Sobel, in Ultrasound in Medicine, Vol. 3, D. White, ed. (Plenum Press, New York, 1977) in press. "Phase Cancellation Effects: A Source of Attenuation Artifact Eliminated by a CdS Acoustoelectric Receiver," L.J. Busse, J.G. Miller, D.E. Yuhas, Vol. 3, D. White, ed. (Plenum Press, New York, 1977) in press.